U.S. patent number 4,630,601 [Application Number 06/493,887] was granted by the patent office on 1986-12-23 for bone nail for the treatment of fractures.
This patent grant is currently assigned to Howmedica International, Inc.. Invention is credited to Hans E. Harder, Hermann Kramer.
United States Patent |
4,630,601 |
Harder , et al. |
December 23, 1986 |
Bone nail for the treatment of fractures
Abstract
A bone nail for the treatment of fractures in the proximal femur
zone is disclosed having a distal end portion adapted to be
disposed at the outer surface of the femoral condyle, said end
portion being provided with a coupling portion for engagement with
a driving tool, a proximal end portion adapted to be seated in the
proximal femur, and an arcuately curved portion between the ends,
with the proximal end portion being provided with a rounded-off
thickened portion at the free end thereof.
Inventors: |
Harder; Hans E.
(Probsteierhagen, DE), Kramer; Hermann (Neumunster,
DE) |
Assignee: |
Howmedica International, Inc.
(Kiel, DE)
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Family
ID: |
6740247 |
Appl.
No.: |
06/493,887 |
Filed: |
May 12, 1983 |
Foreign Application Priority Data
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May 18, 1982 [DE] |
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8214493[U] |
Mar 18, 1983 [EP] |
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83102694.3 |
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Current U.S.
Class: |
606/62 |
Current CPC
Class: |
A61B
17/921 (20130101); A61B 17/7208 (20130101) |
Current International
Class: |
A61B
17/92 (20060101); A61B 17/88 (20060101); A61B
17/72 (20060101); A61B 17/68 (20060101); A61F
005/04 () |
Field of
Search: |
;3/1,1.9
;128/92BB,92BC |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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321447 |
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Mar 1975 |
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AT |
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2305441 |
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Aug 1974 |
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DE |
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1428653 |
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Mar 1976 |
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GB |
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562273 |
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Aug 1977 |
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SU |
|
Primary Examiner: Apley; Richard J.
Assistant Examiner: Isabella; David J.
Attorney, Agent or Firm: Knuth; Charles J. Richardson; Peter
C. Akers; Lawrence C.
Claims
We claim:
1. A thin, flexible and resilient bone nail for the treatment of
fractures in the proximal femur zone, comprising a distal end
portion adapted to be disposed at the outer surface of the femoral
condyle, said distal end portion including a coupling portion for
engagement with a driving tool, a proximal end portion adapted to
be seated in the natural femoral head and having a free end, and a
curved intermediate portion between said end portions, with said
proximal end portion being provided at the free end thereof with a
rounded-off thickened portion having a flattened proximal surface
angulated at such a non-perpendicular angle with respect to the
segment of said proximal end portion immediately adjoining said
rounded-off thickened portion that said surface lies approximately
normal to the direction of physiological loading of the natural
femoral head when said proximal end portion is seated therein in
use.
2. A bone nail of claim 1 wherein said thickened portion is shaped
in the form of a bead.
3. A bone nail of claim 1 wherein the cross section of the nail is
polygonal over its length with edges rounded off.
4. A bone nail of claim 3 wherein said nail is configured to lie
substantially within a single plane of curvature, said intermediate
portion is continuously curved concavely towards a direction that
is substantially the medial direction when the nail is implanted,
and the cross sectional configuration of said nail is an
equilaterial triangle having an axis disposed in said plane of
curvature of the nail extending from an apex located on the medial
side of the nail.
5. A bone nail of claim 3 wherein said nail is configured to lie
substantially within a single plane of curvature and the cross
sectional configuration of said nail is rectangular with the major
axis disposed in said plane of curvature of said nail.
6. A bone nail of claim 4 wherein the side of said equilateral
triangle opposite said apex, said side being located on the lateral
side of said nail, is circularly convexly curved in said cross
section.
7. A bone nail of claim 5 wherein said nail is configured to be
substantially within a single plane of curvature and a throughbore
is provided at the distal end of said nail, the axis of which
throughbore is disposed in said plane of curvature of said
nail.
8. A bone nail of claim 3 wherein the cross-sectional configuration
of the distal end portion of the nail is identical to the
cross-sectional configuration of the remainder of the nail except
for said rounded-off thickened portion and a recess provided in
said distal end portion spaced at a distance from the distal tip of
the nail, said recess forming a reduced gripping portion which is
polygonal in cross section.
9. A bone nail of claim 8 wherein said nail is configured to lie
substantially within a single plane of curvature, said intermediate
portion is continuously curved concavely towards a direction that
is substantially the medial direction when the nail is implanted,
and the cross sectional configuration of said nail is an
equilateral triangle with edges rounded off having an axis disposed
in the plane of curvature of the nail extending from an apex
located on the medial side of the nail, with the cross section in
said reduced gripping portion being a four-sided figure coincident
with said equilateral triangle but excluding a medial triangular
area including said apex.
10. A bone nail of claim 9 wherein the bottom of said recess
extends approximately in parallel with the side of said nail
opposite said apex.
11. A bone nail of claim 1 wherein said nail is configured to lie
substantially within a single plane of curvature and the cross
sectional configuration of said nail is approximately that of a
Maltese cross over its length with edges rounded off, with an axis
of said cross disposed in said plane of curvature of said nail.
Description
BACKGROUND OF THE INVENTION
The invention relates to a bone nail for the treatment of fractures
in the proximal femur zone, comprising a distal end portion
disposed at the outer surface of the femoral condyle, said end
portion being provided with a coupling portion for engagement with
a driving tool, a proximal end portion seated in the proximal femur
and an arcuately curved portion between the ends.
Such a nail is known (West German Pat. No. 23 41 439; West German
Utility Model No. 7 218 224). It is normally used together with
several such nails (bunch nailing). The individual bone nails
consisting of metal are provided with a diameter such that they are
sufficiently elastic, so that they may be driven into the medullary
canal of the femur via a window in the condyle of the femur. The
proximal end of the nail seeks its way in the medullary canal and
arrives in the femoral head via the femoral neck. The distal end of
the nail is designed in such a manner that it is adapted to be
brought into engagement with a drive-in tool. The bone nail is
driven onward in the medullary canal with the aid of the drive-in
tool while being watched on an image amplifier, with the first nail
in particular having to be more or less rotated for repositioning
the bone fragments. The powerful engagement of the drive-in tool at
the distal end of the nail, thus, must be in a position also to
transfer a substantial amount of torque onto the nail.
The known bone nails suffer from some disadvantages. The
flattenings at the distal end which are oriented transversely to
the axis of curvature and which are in addition provided with an
aperture for the purpose of obtaining an effective engagement of a
drive-in tool, may be effective in the manner of a chisel if they
do not come to lie completely flat against the bone and in parallel
therewith, respectively. The relatively sharp edges formed in this
manner may have an irritating effect on the adjacent tissue. As the
flattenings are normally formed in an upsetting process, additional
processing is required so as to remove any burrs or sharp edges
formed in said upsetting step. Through the flattening of a round
nail cross sectional area, in addition, a critical zone of
transition will form having a relatively high notch effect, so that
with a considerable amount of torque applied at the distal end a
plastic deformation or even a shearing off may be the result in
this zone. Upon rotation of the distal ends against each other,
several flattened distal ends require a relatively great amount of
space, whereby the well-being of the patent may be affected.
So that the known nail bones may be driven onward more easily in
the medullary canal it is known to taper them at the proximal end.
Owing thereto, however, the danger exists that the proximal ends in
the enck or in the head zone may protrude and enter the hip bone
and the acetabulum, respectively, which is to be considered to be a
serious complication of the method of treatment rendering it
ineffective.
SUMMARY OF THE INVENTION
It is therefore the object of the invention to provide a bone nail
for the treatment of fractures in the proximal femoral zone by
which it is ensured that inadvertent injuries of the bone in the
zone of the proximal femur will not occur.
This object is attained in accordance with the invention in that
the proximal end portion at the free end is provided with a
rounded-off thickening. Even though such a thickening doubtless
increases the power of driving-in for the individual nail, this
may, on the other hand, be readily taken into bargain because, with
the measure according to the innovation it is avoided that the
proximal end of the nail when being threaded into the neck or head
zone of the femur, injures the femur in that zone by penetrating
into, and through the corticalis, respectively. The increased
driving power, in relation to that one necessary with a point at
the proximal end, lies nevertheless within a range which, with the
up to now usual operational techniques for such bone nails may
doubtless be accepted.
It goes without saying that the thickening is uniformly rounded in
order to avoid injuries. According to one embodiment of the
invention, the thickening is formed in the manner of a bead. It is
preferably provided by upsetting the proximal nail end.
The plane of curvature of the bone nail lies approximately in the
plane extending between the femur shank and the femur neck. The
introduction of forces into the implanted nail essentially is in
parallel with the femur shank and thus onto the proximal end of the
nails, thereby exerting on the curved proximal end portion a torque
in the plane of the curvature. The load on the nails thus is
largely a bending load. For this reason, a pointed proximal end has
a negative effect, because only a small area is provided for the
engagement of forces. Likewise, in this regard a thickening at the
proximal end brings about an improvement, with the area available
for the engagement of forces being substantially increased. In this
connection provision is made in another embodiment of the invention
for a flattening to be provided at the free end of the thickening,
the plane of which extends at an angle with respect to the axis of
the proximal nail end in such a manner that it lies approximately
normal to the direction of loading. That means that the flattening,
the areal dimension of which may obtain a considerable measure
relative to the nail cross sectional area, approximately lies
normal to the femur axis and thus also normal to the direction of
loading.
The known bone nails are circular in cross section. For the moment
of resistance the bone nails are required to provide, however, the
nail diameter in the plane of curvature is largely decisive. That
means that the nail may be reduced in a direction normal to the
axis of curvature, without thereby substantially influencing the
moment of resistance. With nail cross sectional areas formed in
this manner, quite considerable reduction of nail material may be
achieved. In this connection, provision is made in another
embodiment of the invention for the cross sectional area of the
nail to be polygonal over the length thereof with edges rounded
off. But here, preferably, the main axis lies in the plane of
curvature. In another embodiment of the invention it is proposed in
this connection that the cross sectional area be triangular,
preferably in the form of an equilateral triangle. With this cross
sectional shape too, material is saved without markedly reducing
the moment of resistance vis-a-vis a nail having a comparable
circular cross sectional area. As the edges of the triangular cross
sectional area are markedly rounded off, there exists also no
danger of injury in the medullary canal. It is furthermore also
readily guaranteed that the nail may be rotated for purposes of
repositioning and driving-in. A triangular cross sectional
configuration, however, offers the additional advantage that
narrower packaging is possible than with a circular cross sectional
configuration, so that in a given case more nails may be driven in
than bone nails having a circular cross sectional configuration.
The overall moment of resistance with a given cross sectional area
of the medullary canal may be adjusted to be higher than with round
nails.
In another embodiment of the invention provision is made for the
cross sectional area to be rectangular with the major axis lying in
the axis of curvature. With such a cross sectional configuratuion
the saving of material is still greater.
A space-saving arrangement of the distal nail ends results if the
radial extension of the distant end does not exceed that one of the
remaining nail, i.e. the outer contour of the nail does not enlarge
in the distal end zone. In this connection provision is made in
another embodiment of the invention for a bore to be provided at
the distal end, preferably a throughbore, the axis of which
preferably lies in the plane of curvature. A portion of the
drive-in tool may be brought into engagement with the bore, so that
a torsion may be applied to the distal nail end.
Alternatively, it is proposed according to another embodiment of
the invention that a recess be formed spaced through a distance
from the distal end so as to form a clamping section of a polygonal
cross sectional shape. With a polygonal cross sectional shape of
the nail a recess would not be necessary in view of the application
of a rotational force. A recess, however, offers the advantage that
effective pull-out forces may be applied thereby also onto the
nail.
Advantageous further emobodiments of a set of instruments according
to the invention for driving-in the nail according to the invention
are indicated in further subclaims.
DETAILED DESCRIPTION OF THE INVENTION
Some examples of embodiments of the invention are going to be
described in the following in more detail by way of drawings.
FIG. 1 shows a sectional view of a femur having three nails
according to the invention implanted therein.
FIG. 2 shows a lateral view of the distal end of a bone nail
according to FIG. 1.
FIG. 3 shows a sectional view of the nail according to FIG. 2 taken
on line 3--3.
FIG. 4 shows another profile of a bone nail according to the
invention.
FIG. 5 shows a further profile of a bone nail according to the
invention.
FIG. 6 shows an example of embodiment of a proximal end of the bone
nail according to FIG. 1.
FIG. 7 shows a fore-stroke apparatus for a bone nail according to
the invention.
FIG. 8 shows a sectional view of the front portion of the apparatus
according to FIG. 7.
FIG. 9 shows an after-stroke aparatus for a bone nail according to
the invention.
FIG. 10 shows a view of the rear end of the apparatus according to
FIG. 9 rotated through 90.degree..
FIG. 11 shows a front view of the apparatus according to FIG.
9.
FIG. 12 shows a sectional view of the apparatus according to FIG. 9
taken on line 12--12.
FIG. 13 shows a cross sectional view of another embodiment of a
nail.
Prior to enlarging on the individual representations shown in the
drawings let it be stated that each of the features described and
shown is of inventively essential importance by itself or in
connection with features of the claims.
The three bone nails implanted in a femur 10 are generally
referenced 11. They are provided with a continuous curvature
starting out from the proximal end, as shown at 12. In the zone of
the distal end a bend 13 is formed which is followed by a straight
piece 14. The bone nails 11 have been driven in via a window 15 of
the medial condyle of the femur 10 as shown, with the aid of a
drive-in tool. i.e. one bone nail after the other. The nail first
driven in normally serves to reposition the segment of fracture.
The introduction of the bone nails is performed under control with
the aid of an image amplifier, so that a fanning out may be
obtained in the head region of the femur, thereby achieving a
certain rotary stability of the head relative to the remaining
femur. The proximal end portions are provided with thickenings,
generally referenced 16 in FIG. 1.
As may be recognized from FIG. 3, the cross sectional configuration
of the nails 12 is an equilateral triangle, having the edges
thereof considerably rounded off at the corners as shown at 17. One
side 18 in this arrangement forms the convex side of the curvature
12, while the opposite edge 19 is disposed on the concave side of
the nail 11.
As indicated by the circle 20 drawn in broken lines, the nail 11
brings about a considerable material saving as opposed to a nail
having a circular cross sectional area 20, without the moment of
resistance being substantially reduced. The cross sectional
configuration shown in FIG. 3, in addition, offers the advantage
that the nails may be better "packed" in the medullary canal.
As is furthermore to be derived from FIGS. 2 and 3, a recess 21 is
formed in the straight distal end portion 14 the bottom of said
recess extending approximately in parallel with the side 18 of the
nail 11. A drive-in tool may be brought into engagement with the
recess 21 in order to drive the nail forward in the medullary canal
or extract it from the medullary canal, and perform during these
movements, in addition, a rotary movement. The remaining cross
sectional area 23 easily suffices to withstand forces of rotation.
In this arrangement, it is recommendable to select the transition
of the cross sectional area 23 into the triangular full cross
sectional area to be a steady one, so as to avoid unnecessarily
high notching forces.
It will be noted from FIGS. 2 and 3 that despite a coupling section
for a drive-in tool the outer contour of the remaining nail is not
departed from, therefore, there are no projecting parts
unnecessarily increasing the space and affecting the tissue.
FIG. 4 shows a bone nail 30 in a cross sectional view which is
approximately rectangularly shaped with edges 31 likewise strongly
rounded off. The plane of curvature coincides with the major axis
32 of the rectangular cross sectional configuration. The bone nail
30 has a moment of resistance comparable to that of a bone nail
having a circular cross sectional configuration as indicated by the
circle 33 shown in broken lines. The former, therefore has for a
result a considerable material saving without the bearing capacity
thereby being reduced.
FIG. 5 shows a nail 35 approximately having the shape of a Maltese
cross in cross section, with the edges again being strongly rounded
off as shown at 36. Here as well a circle 37 shown in broken lines
shows a circular cross section of a bone nail having a moment of
resistance which is comparable to that of the bone nail 35.
In FIG. 6, the bone nail 11 is shown with the proximal end portion.
There will be recognized a bead 16 of enlarged diameter having an
approximately circular outer contour. Furthermore, the bead is
flattened at the free end thereof, as shown at 40. This flattening
lies in a plane which extends approximately vertically with respect
to the direction of leading which is indicated by an arrow 41. Said
arrow 41 is also shown in FIG. 1.
It goes without saying that additionally the portion 23 is provided
with a bore or throughbore 23', respectively, in order to improve
the power engagement with a drive-in tool. A throughbore at the
distal end may, by the way, be shaped with any cross sectional
configuration, in order to have a drive-in and extraction tool
engage thereat.
In FIG. 2 a bore is indicated at 23" which is arranged outside the
recessed portion 21 facing the end. A bore arranged transversely
thereto is designated with 23"' in FIG. 3.
The nail has, besides, a straight portion at the distal end portion
which is connected to the remaining nail through a wide arc.
FIGS. 7 and 8 show a fore-stroke drive-in apparatus for bone nails
shown in FIGS. 1 to 6. Said apparatus consists of a gripping
portion 45 and a coupling portion 46. Both of them comprise an
elongated shank 47 of a circular cross sectional configuration
provided with a transverse bar 48 in the gripping portion 45 which
is guided through a corresponding bore. A coupling lever 49 is
pivotally supported in the coupling portion 46 (FIG. 8) with the
aid of a bearing pin 50. For the purpose of accommodating the
coupling lever 49 a slot 51 is formed axially in the shank 47 which
accommodates the relatively narrow coupling lever 49, so that is
projects but little over the outer contour of the shank. The
coupling lever 49 extends as far as the end of the shank 47
spanning a recess 52 of triangular cross sectional configuration
which opens towards the end of the shank 47 and is defined by an
abutment wall 53 at the opposite end having a transverse groove 54
situated at the foot portion thereof. A journal 55 recessed into
the shank 47 projects upwards into the recess 52.
A blind bore 56 is provided in the bottom of the slot 51 which
accommodates a compression spring 57 biasing the coupling lever 49
in a clockwise sense. The slot 51 is provided with an interruption
58 in a diametrically downward direction for the accommodation of a
cam 59 of a clamping lever 60. The clamping lever 60 is pivotally
supported in the region of the cam 59 with the aid of a bearing
journal 61, said levers 49 and 60 being pivotable approximately in
one and the same plane. A center portion of the lever 60 is in part
accommodated in a recess 62 of the shank 47. A handling means 63
extends obliquely outwards.
In the position as shown in FIG. 8 the coupling lever 49 is locked
by the clamping lever 60. The highest point of the cam 59 is
disposed opposite to the axis of rotation of the journal 61 in
offset arrangement with respect to the pivotal journal 50. The
spring 57 tends to rotate the coupling lever 49 in a clockwise
direction. Thereby, the portion of the lever 49 shown to the right
in FIG. 8 exerts a pressure on the cam 59 from above and biases the
clamping lever 60 in a counterclockwise direction. A pivotal
movement of the clamping lever 60 in this direction, however, is
not possible because it is limited by the shank 57 and the recess
62, respectively. Only when the handling means 63 is engaged by
hand and the clamping lever 60 is likewise rotated in a clockwise
direction may the coupling lever 59 likewise pivot in a clockwise
direction. Thereby the distal end of a bone nail may be inserted
into the recess 42 with the journal 55, for example, engaging in
the recess 21 of a bone nail according to FIGS. 1 to 3. A bone nail
thus accommodated may now be driven in with the aid of the
fore-stroke tool according to FIGS. 7 and 8 and be manipulated in
the manner as desired and may, for example, also be withdrawn again
entirely or in part. An inadvertent loosening of the apparatus from
the bone nail is avoided by the clamping device as described
above.
As it is difficult especially with several nails to wholly drive-in
the bone nail with the aid of the fore-stroke drive-in apparatus
according to FIGS. 7 and 8, an after-stroke apparatus is provided
in accordance with FIGS. 9 to 12. The after-stroke apparatus
comprises an elongated shank 65 of an approximately circular-shaped
cross sectional configuration which is slightly cranked at 66 in
the region of the forward third thereof. The shank 66 tapers
steadily towards the front end. At the front end thereof it is
provided with a forwardly opening recess 67 the cross section of
which is adapted to the cross section of the distal end, i.e. is
triangularly shaped, for example, as shown in FIG. 11. The gripping
portion proper is provided with longitudinally extending
corrugations 68, so that the after-stroke apparatus may be better
seized by hand. In the rearward zone thereof the shank 65 has an
outward opening transversely extending slot 69 formed therein. A
throughbore 70 is furthermore provided to extend in parallel
therewith (FIG. 10). The slot 69 and the throughbore 70
respectively have a width and diameter slightly greater than the
greatest diameter of the bone nail. The apparatus according to
FIGS. 9 to 12 may therefore also serve as a so-called setting iron
with the aid of which it is possible to deform the bone nail in a
limited way, that is to impart thereto a different curvature, for
example, or a different direction. Preferably, two such apparatuses
are employed in this operation.
The point of the after-stroke apparatus may be provided with a
milling or flattening at the underside thereof so as to be able to
engage within the groove 21 of the nail 11 for purposes of bearing
out. In this manner the implanted nail may be beaten out so far
that the fore-stroke drive-in tool may be employed.
The profile of the nail 80 according to FIG. 13 is indeed likewise
triangularly shaped, on principle, as is the one according to FIGS.
1 to 3. The convex side 81, however, is not straight but is crowned
in cross section. The relatively large radius of the side 81
results in a soft transition towards the radii at the edges of the
nail 80. Also the concavely extending edge 82 is provided with a
radius.
* * * * *